An electronic expansion valve is an important component in a refrigerating/heating system, and is primarily used to regulate flow rate of refrigerant fluid. A conventional electronic expansion valve generally includes a drive mechanism (e.g. a step motor), an actuation mechanism (e.g. a threaded screw rod mechanism), a throttle mechanism (e.g. a valve needle and a valve seat) and related auxiliary mechanism.
However, a conventional electronic expansion valve, after de-energized, cannot close automatically since a driving force applied to the threaded screw rod mechanism is eliminated. Hence, in order to break the fluid circuit securely, an independent electromagnetic switch valve (which is generally a normal close valve, switches on when being energized, and switches off when being de-energized) is generally connected in series at upstream or downstream of the electronic expansion valve. In this way, when the system is de-energized, the electromagnetic switch valve will switch off automatically to break the fluid circuit.
However, if the above configuration is adopted, on the one hand, the total cost of the system is increased since an independent electromagnetic switch valve is additionally provided, and one the other hand, in order to connect in series the electromagnetic switch valve, two braze welding joints (i.e., at an inlet and an outlet of the electromagnetic switch valve) will be additionally provided in the pipeline, which not only increases the assembling cost of the system, but also increases the risk of leakage of the system.
Another method for achieving automatic closing of an electronic expansion valve after de-energized is to provide the electronic expansion valve with a standby power supply, for example, to additionally provide a super-capacitor for storing electric energy or be equipped with a standby battery on a control board of the electronic expansion valve. However, this method also increases cost of the electronic expansion valve and requires a more complicated controller.
Therefore, an electronic expansion valve which may close automatically after de-energized is desired.